Blood and the Cardiovascular System

Comprehensive practice flashcards covering the components, characteristics, cellular formed elements, blood typing systems, and hemostatic mechanisms of human blood.

Blood

A specialized connective tissue containing formed cells and cell fragments suspended in a liquid fluid matrix called plasma.

Cardiovascular System

An organ system consisting of the fluid component (blood), a muscular pump that circulates it (the heart), and conducting passageways that distribute it throughout the body (blood vessels).

Plasma

The liquid extracellular matrix of blood, constituting approximately $55\%$ ($46\text{--}63\%$) of whole blood volume; composed of $92\%$ water, $7\%$ plasma proteins, and other dissolved solutes.

Formed Elements

The cellular structures and fragments suspended in blood plasma, accounting for roughly $45\%$ of whole blood; includes erythrocytes, leukocytes, and platelets.

Fractionation

The laboratory procedure used to separate whole blood into its liquid plasma component and cellular formed elements.

Buffy Coat

The thin, whitish intermediate layer that forms between packed red blood cells and plasma during centrifugation, composed of white blood cells and platelets ($<1\%$ of whole blood).

Hematocrit

The percentage of whole blood volume composed of packed red blood cells, normally ranging from $37\%$ to $54\%$ in healthy adults.

Albumins

The most abundant plasma proteins ($60\%$ of total plasma protein content), synthesized primarily by the liver; responsible for maintaining osmotic pressure and transporting fatty acids and thyroid and steroid hormones.

Globulins

Plasma proteins constituting approximately $35\%$ of total plasma proteins; includes antibodies (immunoglobulins) produced by white blood cells for immune defense, as well as transport proteins.

Fibrinogen

A soluble plasma protein comprising about $4\%$ of plasma proteins, synthesized by the liver; serves as the precursor converted into insoluble fibrin strands during blood coagulation.

Hemopoiesis

The continuous physiological process through which all blood formed elements—erythrocytes, leukocytes, and platelets—are developed and produced.

Erythrocytes

Biconcave, anucleate formed elements that make up $99.9\%$ of all formed elements; packed with hemoglobin to transport oxygen and carbon dioxide between the lungs and peripheral tissues.

Hemoglobin

A complex quaternary respiratory protein consisting of two alpha ($\alpha$) and two beta ($\beta$) polypeptide chains, each bound to an iron-containing heme pigment group, transporting $98.5\%$ of blood oxygen.

Heme

An iron-containing ring structure embedded within each hemoglobin polypeptide subunit that reversibly binds a single molecule of oxygen ($\text{O}_2$).

Oxyhemoglobin

The bright red chemical complex formed when oxygen reversibly binds to the iron atom in hemoglobin.

Deoxyhemoglobin

A darker red hemoglobin molecule that has released its bound oxygen to surrounding tissues.

Carbaminohemoglobin

The molecular complex formed when carbon dioxide ($\text{CO}_2$) binds directly to the amino acid chains of hemoglobin rather than to the heme group.

Erythropoiesis

The developmental process of red blood cell formation, occurring exclusively in the myeloid tissue of red bone marrow in adults.

Erythropoietin (EPO)

A glycoprotein hormone synthesized and released primarily by the kidneys in response to tissue hypoxia that stimulates red bone marrow stem cells to produce red blood cells.

Blood Doping

The illicit enhancement of athletic endurance through the administration of erythropoietin ($\text{EPO}$), testosterone, or homologous/autologous packed red blood cells to elevate hematocrit.

Leukocytes

Complete nucleated white blood cells that defend the body against pathogens, toxins, and foreign invaders, capable of amoeboid movement and emigration from capillaries.

Chemotaxis

The directed amoeboid migration of white blood cells along a chemical concentration gradient toward areas of tissue damage, infection, or inflammation.

Neutrophils

Polymorphonuclear granulocytes with multilobed nuclei ($3000\text{--}7000\,\mu\text{l}^{-1}$; $50\text{--}70\%$ of circulating leukocytes); highly mobile, aggressive phagocytes that serve as the first responders to bacterial invasion.

Eosinophils

Granular leukocytes ($100\text{--}400\,\mu\text{l}^{-1}$; $2\text{--}4\%$ of circulating leukocytes) with bilobed nuclei and bright red granules; destroy parasitic worms via toxic exocytosis and suppress allergic inflammatory responses.

Basophils

Rare granular leukocytes ($20\text{--}50\,\mu\text{l}^{-1}$; $<1\%$ of circulating leukocytes) with bilobed nuclei obscured by coarse blue-purple granules; promote inflammation by releasing histamine and heparin.

Histamine

An inflammatory vasoactive chemical released by activated basophils and mast cells that promotes vasodilation and increases capillary permeability.

Heparin

An anticoagulant polysaccharide secreted by basophils and mast cells to inhibit local blood clotting during initial inflammation.

Monocytes

Large agranular leukocytes ($100\text{--}700\,\mu\text{l}^{-1}$; $2\text{--}8\%$ of circulating leukocytes) with kidney-shaped nuclei; circulate briefly before migrating into peripheral tissues to become long-lived phagocytic macrophages.

Lymphocytes

Agranular leukocytes ($1500\text{--}3000\,\mu\text{l}^{-1}$; $20\text{--}40\%$ of circulating leukocytes) characterized by a large round nucleus with a thin rim of pale blue cytoplasm; mediate adaptive immunity.

Cytotoxic T Cells

$\text{CD8}^+$ T lymphocytes responsible for cell-mediated immunity; directly recognize, attack, and destroy foreign, virus-infected, or abnormal host cells.

Helper T Cells

$\text{CD4}^+$ T lymphocytes that regulate and coordinate the adaptive immune response by releasing cytokines that stimulate both cytotoxic T cells and B cells.

B Cells

Lymphocytes responsible for humoral (antibody-mediated) immunity that differentiate into plasma cells to synthesize and secrete specific circulating antibodies.

Natural Killer (NK) Cells

Large granular lymphocytes that execute immunological surveillance by identifying and destroying abnormal cells that lack normal surface MHC class I markers, such as cancer cells and virus-infected cells.

Platelets

Small, discoid, anucleate cytoplasmic cell fragments ($150{,}000\text{--}500{,}000\,\mu\text{l}^{-1}$) derived from megakaryocytes; essential for hemostasis and vascular repair, with a lifespan of $5\text{--}10$ days.

Megakaryocytes

Large, polyploid hematopoietic precursor cells resident in the red bone marrow that continually shed cytoplasmic fragments into capillaries to generate circulating platelets.

Antigen

A surface molecule or chemical marker (typically a protein or carbohydrate) capable of triggering a targeted immune response by lymphocytes.

Antibody

A defensive, Y-shaped plasma protein (immunoglobulin) produced by B-cell-derived plasma cells that selectively recognizes, binds, and neutralizes a specific antigen.

ABO Blood Group

A genetically determined blood classification system based on the presence or absence of inherited antigen A and antigen B glycolipid markers on the surface of erythrocytes.

Rh Blood Group

A blood classification system determined by the presence ($\text{Rh}^+$) or absence ($\text{Rh}^-$) of the Rh surface protein, specifically antigen D, on red blood cells.

Agglutination

The cross-linking and clumping together of erythrocytes that occurs when circulating plasma antibodies bind to corresponding surface antigens on incompatible donor red blood cells.

Universal Donor

An individual with type $\text{O}^-$ blood whose red blood cells lack A, B, and Rh surface antigens, allowing their packed erythrocytes to be transfused with minimal risk of ABO/Rh agglutination.

Universal Recipient

An individual with type $\text{AB}^+$ blood whose plasma lacks anti-A, anti-B, and anti-Rh antibodies, enabling them to receive red blood cells of any ABO/Rh blood type safely.

Hemostasis

The physiological sequence of processes that arrests blood loss from a damaged vessel; consists of the vascular phase, platelet phase, and coagulation phase.

Vascular Spasm

The rapid, local contraction of vascular smooth muscle in response to vessel injury, immediately narrowing the vessel lumen to diminish blood flow and minimize blood loss.

Platelet Phase

The second stage of hemostasis, in which circulating platelets adhere to exposed subendothelial collagen fibers and aggregate to construct a temporary platelet plug.

Prostacyclin

A prostaglandin derivative produced and released by healthy vascular endothelial cells that actively inhibits platelet aggregation, confining the platelet plug to the site of injury.

Coagulation Phase

The third stage of hemostasis involving an enzymatic cascade of plasma proenzymes (clotting factors) that converts soluble fibrinogen into an insoluble fibrin meshwork to produce a stable clot.

Extrinsic Pathway

A rapid clotting cascade initiated by trauma to tissues outside the bloodstream, triggering the release of tissue thromboplastin (Factor $\text{III}$), which combines with Factor $\text{VII}$ and $\text{Ca}^{2+}$ to activate Factor $\text{X}$.

Intrinsic Pathway

A slower clotting cascade initiated within the bloodstream when Factor $\text{XII}$ (Hageman factor) makes contact with negatively charged surfaces or exposed subendothelial collagen, ultimately activating Factor $\text{X}$.

Common Pathway

The terminal sequence of blood clotting beginning with activated Factor $\text{X}$, which forms prothrombinase to convert prothrombin (Factor $\text{II}$) into active thrombin, which then converts fibrinogen into insoluble fibrin.

Thrombin

An active serine protease enzyme generated from prothrombin that cleaves soluble fibrinogen into insoluble fibrin monomers and activates Factor $\text{XIII}$ to stabilize the fibrin meshwork.

Fibrin

An insoluble, thread-like fibrous protein assembled into an interwoven mesh that traps circulating blood cells and platelets, forming the structural basis of a definitive blood clot.

Thrombocytopenia

A hematologic disorder defined by an abnormally low circulating platelet count ($<150{,}000\,\mu\text{l}^{-1}$), impairing normal clot formation and predisposing patients to uncontrolled bleeding.

Hemophilia

An inherited genetic bleeding disorder caused by a quantitative deficiency or qualitative defect in specific blood clotting factors, resulting in impaired coagulation.

Thrombophilia

A medical condition characterized by hypercoagulability or an elevated tendency to develop inappropriate arterial or venous intravascular blood clots.